The present invention relates to the field of wheel rim manufacturing and more particularly to an improved method of manufacturing an aluminum alloy wheel rim.
Methods for making wheel rims are well known. For example, U.S. Pat. No. 4,589,177 to Secolo et al. and U.S. Pat. No. 4,185,370 to Evens both disclosed such methods. The method of Evans""s Patent is illustrated in FIGS. 1 to 3. In FIG. 1, a strip 1 of aluminum sheet material used to form a wheel rim is shown. In FIG. 2, such strip 1 is formed into a hoop 3 and the opposing ends flash butt welded forming weld line 2. The thus formed hoop is subsequently passed through multiple forming operations (e.g., press and roll forming operations) resulting in a finished wheel rim 4 having desired sectional profiles shown in FIG. 3.
But this is unsatisfactory for the purpose for which the invention is concerned for the following reasons: Firstly, a variety of expensive rollers are employed in the roll forming operations in order to manufacture a wheel rim having desired sectional profiles. Further, such manufacturing processes are complex, time consuming, labor intensive, and excessive energy consumption. This results in an increase of manufacturing cost. Secondly, as stated above a series of forming operations (e.g., press and roll forming operations) are performed on the hoop to form a wheel rim having desired sectional profiles. But the formed wheel rim may be deformed or too thin due to non-uniform pressing in these manufacturing processes. As a result, the formed wheel rim is unbalanced in weight or unacceptable low in hardness, thus adversely shortening the useful life of wheel rim. Thus improvement exists.
It is therefore an object of the present invention to provide a method of manufacturing a wheel rim for a motor vehicle comprising the steps of (a) forming a strip of aluminum alloy sheet material having a predetermined cross-section suitable for forming into a wheel rim by extrusion molding; (b) pressing the strip step-by-step lengthwise by an upper mold and a lower mold having complimentary profiles for causing the strip to have predetermined profiles as a hoop with a formed gap between the both ends; (c) welding the gap to form an unfinished wheel rim; and (d) annealing, shaping, heat treating, and polishing the unfinished wheel rim to form a finished wheel rim.